The development of interactions of full-term and premature infants with their mothers during the first year of life is studied in a black inner-city sample. Just prior to the time the infants leave the hospital and when the infants are one month, three months, and twelve months old, mothers and infants are observed during a 30-minute session which includes a feeding. A detailed sequential record of this interaction is made using a code catalog of some 60 infant and 60 mother behaviors. The Prechtl Neurological Examination and the Brazelton Behavioral Assessment Scale are administered to all newborns. The Brazelton Neonatal Behavioral Assessment Scale is administered when the infants are one month of age and the Bayley Scales of Infant Development are administered when they are three months and twelve months of age. Sociological background data are collected from all mothers and the Inventory of Home Stimulation, developed by Caldwell, Heider, and Kaplan (1966), will be used to assess the quality of the infants' home environment when the infants are nine months old. These normative data will be analyzed to identify abnormal interactions and to describe infant behaviors which correlate with such abnormal interactions. Intervention programs consisting of infant stimulation alone, mother training alone, and both will be developed for premature infants on the basis of the normative data. The relative effectiveness of these programs to improve mother-infant interaction will be evaluated.